The consulting firm is filled with so many former bureaucrats and political insiders that it has become known as Wall Street’s shadow regulator.

Nearly two-thirds of its roughly 170 senior executives worked at agencies that oversee the financial industry. The founder, Eugene A. Ludwig, is a former comptroller of the currency and a law school friend of Bill Clinton; the latest hire, Mary L. Schapiro, ran the Securities and Exchange Commission until late last year.

Building off those connections, the Promontory Financial Group has emerged as a major power broker in Washington, helping Wall Street navigate an onslaught of new rules and regulatory scrutiny. Promontory accompanied Morgan Stanley when the bank urged regulators to rethink limits on risky trading, records show. It also joined Bank of America, Citigroup and other big banks at the Treasury Department to discuss plans for dismantling failing financial firms.